Recent findings indicate that cadaverine and some of its metabolites are associated with schizophrenia. It was demonstrated on three separate groups of subjects that blood levels of monoacetylcadaverine and monopropionylcadaverine were elevated in schizophrenic patients in comparison to those in healthy controls. Based on their blood concentrations of acylcadaverines, more than 90% of subjects could be classified in agreement with the clinical diagnosis of schizophrenia. It has been suggested that the blood levels of monoacetylcadaverine and monopropionylcadaverine may be used for an objective, biochemical classification of mental patients and perhaps even as a metabolic clue to some mental disorders. It is the purpose of this study to experimentally support or refute the above assumption. Cadaverine, monoacetylcadaverine, and monopropionylcadaverine will be measured in the blood of groups of a) mental patients, b) neurological patients, c) patients hospitalized for other reasons than in the previous two groups (nonneurological, nonpsychiatric), and d) apparently healthy subjects. The assay will be performed by a combined thin-layer chromatography-high resolution mass spectrometry method, using reversed peak-matching for mass identification and an integrated ion current technique for quantification of studied substances. The activities of enzymes involved in the synthesis of acylcadaverines (i.e., acetyl-CoA:1,5-diaminopentane N-acetyltransferase and propionyl-CoA:1,5-Diaminopentane N-propionyltransferase) will be measured in the blood buffy coat fraction. The activity of monoamine oxidase, the enzyme that catabolizes acylcadaverines, will be measured in the blood platelets.